RLS: setup for v0.12.0

[mmcky]

Sets up the v0.12.0 release: bumps __version__, adds the CHANGELOG pointer to the GitHub release notes, and records version and date-released in CITATION.cff so citation exporters pick up the snapshot.

Why a minor bump

main carries 29 merged PRs since v0.11.4 (15 July), 16 of them touching shipped code, and several are not patch-level. #833 ships .. deprecated:: 0.12.0 directives for tic/tac/toc/loop_timer, so the next tag has to be 0.12.0 to match. #864 raises requires-python to >=3.12 and removes the importable quantecon.util.common_messages. #947 drops sympy as a runtime dependency. #832, #940 and #917 add public API: DiscreteDP.state_values, DiscreteDP.action_values, util.index_dict and random.draw(rng=...).

Release-notes items to add by hand

The notes are generated from PR titles, which hide these. Paste them under a "Breaking changes" heading when publishing the release:

• requires-python is now >=3.12 (DOC: repo-wide documentation consistency audit #864). Users on older interpreters stop resolving new releases.
• sympy is no longer a runtime dependency (MAINT: Remove the sympy dependency #947).
• quantecon.util.common_messages is removed (DOC: repo-wide documentation consistency audit #864). It held one string for a Numba-fallback path that no longer exists, and nothing imported it.
• tic, tac, toc and loop_timer now emit DeprecationWarning (DEPR: deprecate Matlab-like tic/tac/toc/loop_timer timers (#786) #833). Use the Timer context manager and timeit instead; removal is scheduled for v1.0 and tracked in MAINT: remove the deprecated tic, tac, toc and loop_timer timers (v1.0) #786.
• Repository-only removals, no package impact: docs/sphinxext/ and MANIFEST.in (DOC: repo-wide documentation consistency audit #864).

After merge

1. Tag v0.12.0 on main. The Publish to PyPI job in ci.yml runs on v* tags.
2. Edit the generated release notes with the items above.
3. The conda-forge feedstock recipe still lists sympy, numba >=0.49.0 and an older python_min. The bot's version-bump PR there needs those edited before it merges.
4. WASM: reduce import-time eager Numba compilation #930 stays open for the warm-cache import measurement in JupyterLite, which needs the testbed from WASM: Host a WASM testbed site under the QuantEcon org #950. Its library change landed in WASM: defer Numba gufunc compilation to first call (#930) #957, so the intermediate release planned in WASM: browser support for QuantEcon.py (Numba + JupyterLite) — tracking issue #925 goes ahead without waiting on that measurement.

Notes for review

• The CHANGELOG date is today's. Adjust it if the tag lands on a different day.
• DOC: refresh README install path and CITATION.cff version #971 also adds version and date-released to CITATION.cff (as 0.11.4) alongside README changes. Once this merges it will need a rebase that drops the citation hunk.
• No other files carry the version: docs/source/conf.py reads it from the package, and pyproject.toml declares it dynamic.

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟢 Approval recommended

The version/date updates are consistent across the package, CITATION metadata, and changelog without introducing functional code changes.

Review effort: Lite
Findings: None

What changed in this PR

Sets up the v0.12.0 release metadata across the package, citation file, and changelog so the published tag and citation/export tooling consistently report the new version.

Changes:

• Bump quantecon.__version__ to 0.12.0.
• Record version and date-released for 0.12.0 in CITATION.cff.
• Add a v0.12.0 section to CHANGELOG.md that points to the GitHub release notes for the tag.

File	Description
quantecon/​__init__.py	Updates the package __version__ constant to 0.12.0.
CITATION.cff	Adds top-level version and date-released for citation exporters.
CHANGELOG.md	Adds a v0.12.0 header and link to the GitHub release notes/tag.

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[coveralls]

coverage: 94.0%. remained the same — rls/v0.12.0 into main

[mmcky]

@oyamad I am releasing this due to deprecation notices in tic/tac/toc tied to v0.12.